1. Field of the Invention
This invention relates to the field of video surveillance cameras, and in particular, to a method and apparatus for controlling movement of a video surveillance camera without relying on a continuous axis of rotation.
2. Description of Related Art
Current implementations of video surveillance camera movement apparatus require that one axis of movement be capable of continuous rotation. This is typically the vertical axis, also referred to as the pan axis. This vertical axis allows continuous horizontal positioning of the camera. The horizontal axis, also referred to as the tilt axis, is typically limited to less than 180 degrees of movement. This limitation is not a problem in and of itself, because video surveillance cameras are usually mounted adjacent to ceilings or walls. The required field of view in almost every surveillance situation is substantially hemispherical. In order to implement continuous pan rotation, a mechanism must be included in the camera movement device which allows the passage of power, video signals and data signals as appropriate, between a stationary base and the surveillance camera, through the vertical and horizontal axes. The transmission of signals through a continuously rotating axis is typically accomplished with a slip ring mechanism using electrical brushes and conductive rings. This kind of slip ring mechanism is costly to manufacture, has a limited life and can cause noise in the video and data signals, all of which eventually lead to operating problems with the camera, or degraded video signals, or both.
An alternative solution utilizes radio frequency transmitters and receivers to transmit the video and data signals and air core transformers to couple power. These alternative methods are also costly and are also subject to reliability problems.
A long-felt need exists for a video surveillance camera movement control system which eliminates the need for a continuous rotation axis, and the problems resulting from such structure.